President Felipe Calderón on Friday promised to redouble the fight against crime gangs after 52 people were killed in a fire Thursday at a casino in northern Mexico set by armed men.

RANDAL C. ARCHIBOLD

MEXICO CITY — An arson attack on a casino in northern Mexico on Thursday that left 52 people dead has thrown a spotlight on the growth of gambling houses throughout the country and their role in organized crime.

In what President Felipe Calderón called an act of “true terrorists,” armed men in four vehicles — a Mini Cooper leading sport utility vehicles and a pickup truck — calmly drove up to the Casino Royale in Monterrey at midafternoon, dashed inside, ordered people to get out and set it ablaze with a flammable liquid.

The flash fire engulfed the gaming hall, trapping patrons scrambling for the few exits and hiding in bathrooms. The toll was among the highest for a single attack since a government crackdown on organized crime began in 2006 and infighting among gangs unleashed an explosion of violence that has left more than 35,000 dead.

Although no motive has been determined, it bore the hallmarks of an organized crime assault, and government officials and security analysts said the brutality suggested the work of the Zetas, one of the largest and most feared gangs in the area.

On Friday, Mr. Calderón and, in a statement, President Obama cast the disaster as related to the drug war. Mr. Calderón, in a departure from past mass killings, labeled the attack terrorism.

“It is evident we are not facing common criminals, we are facing true terrorists who have surpassed not only the limits of the law but basic common sense and respect for life,” Mr. Calderón said, his voice tinged with anger.

He went on to scold the Mexican Congress for not enacting security reforms he has proposed, and the United States, which he called an ally, but one whose drug consumption and gun sales have exacerbated the problem in Mexico.

“We are neighbors, we are allies, we are friends, but you, too, share responsibility,” he said.

Mr. Obama released a brief statement condemning “the barbaric and reprehensible attack,” adding, “We share with Mexico responsibility for meeting this challenge, and we are committed to continuing our unprecedented cooperation in confronting these criminal organizations.”

Mexico does not have Las Vegas-style gambling, or more accurately, such gaming houses are technically prohibited by law.

But sports betting, bingo and electronic games are permitted, and many entertainment businesses fashion themselves as casinos, lit garishly outside and dimly inside, while illegal betting parlors operate in the shadows, according to security analysts.

A lot of money flows through such casinos, making tempting targets for organized crime groups, which extort them or launder money through them, the analysts said.

The national magazine Proceso reported in June that both legal and illegal gambling businesses had grown to nearly 800 this year, from just over 100 in 2000. In Nuevo Leon State, where Monterrey is, the number of businesses climbed to 57 this year from 5 a decade ago.

Raúl Benitez-Manaut, a researcher at the National Autonomous University in Mexico City who studies criminal groups, said such gambling halls were typically small, sometimes informal places but had become a magnet for extortionists and money launderers.

George Grayson, a professor at the College of William & Mary in Williamsburg, Va., who has written extensively about organized crime in Mexico, said payments to the gangs could run up to $10,000 a week.

One theory investigators were exploring, Mr. Benitez-Manaut said, was that the Casino Royale’s “owners were paying one group and another group wanted a ‘tax.’ ”

Stratfor, a security consultant company based in Austin, Tex., that studies the cartels, issued a report that said there had been a rash of robberies and violence at casinos in Nuevo Leon in the past few months.

Four, including the Casino Royale, were robbed on May 25 by heavily armed gunmen. In January, gunmen opened fire in the Casino Royale apparently in an effort to eliminate two rivals gambling there.

Its report suggested the robberies and attacks pointed to an effort by the gangs to undermine rivals’ finances and enrich their own. The Zetas are waging a bloody battle against the Gulf and Sinaloa cartels for control of northeast Mexico, turning Monterrey, a once peaceful business hub, into a battleground with spectacular crimes like mass shootings with the bodies of victims hung from overpasses.

“The tit-for-tat operations in which Gulf and Zetas elements target each other’s vital support networks appear to have been elevated to a higher level with bigger stakes,” the Stratfor report said.

The casinos operate under a tangle of local and federal permits, including those issued by the federal Interior Ministry, but local authorities complain regulation is lax, courts have overruled their efforts to close them and they are left with the burden of dealing with the crime that comes with them.

One of the country’s most prominent gaming tycoons, Jorge Hank Rhon, a former mayor of Tijuana, was arrested on weapons charges in June and held briefly before the charges were dropped.

José Francisco Blake Mora, the interior minister, said at a news conference on Friday that it appeared that the Casino Royale, which was owned by Vallarta Attractions and Amusements in association with the Cysma Corporation, had a permit, but that the government would crack down on betting halls operating outside of the law. The ministry said investigators had not been able to locate the owners.

“The Interior Ministry will be very attentive so that these types of establishments that have authorization to operate strictly according to the law, Mr. Mora said, “and for those that don’t, of course, we will take the pertinent measures that we have to be able to close them down.”